(a) Field of the Invention
The present invention relates to an automatic transmission. More particularly, the present invention relates to a shift control method that allows a sport mode shifting request to be performed on the basis of vehicle operation parameters.
(b) Background
Typically, an automatic transmission automatically controls its shifting operation. For such an automatic shifting control, a shift control apparatus controls hydraulic pressure of a plurality of solenoid valves depending on various vehicle operation conditions including vehicle speed and throttle valve opening.
The automatic transmission includes a number of frictional elements. For shifting operation, an off-going element is released from its operation and an on-coming element is newly operated. The operation of the off-going and on-coming elements is conducted through control of hydraulic pressure supplied thereto.
Recently, an automatic transmission is provided with a sport mode. Such transmission can operate just as the common type of automatic transmission, but it also allows the driver to override the automatic mode by moving a shift lever and feel dynamic gear shifting.
More particularly, sport mode can be selected by moving a shift lever to a manual gate (or called a sport mode gate) that is usually arranged to the right of D range position. Such a sport mode gate is typically formed with “+” and “−” positions and a neutral position therebetween, and a shift request is generated by moving the shift lever to the “+” or “−” position. Once moved to the “+” or “−” position, the shift lever can easily return to its neutral position by a returning device installed in the shift lever assembly.
Typically, a downshift request is generated when the shift lever is moved to the “−” position, and such a downshift request in a sport mode is hereinafter called a sport mode down-shifting request. Also, an upshift request is generated when the shift lever is moved to the “+” position, and such an upshift request in a sport mode is hereinafter called a sport mode up-shifting request.
Appropriate operation of the shift lever allows skip shifting. For example, if the shift lever is repeatedly operated twice, the skip shifting such as 5→3 or 2→4 shifting is enabled.
Sport mode provides a better responsiveness than manual transmission, owing to the shortened shifting period and continuous transmission of engine power.
Normally, sport mode does not involve so-called hold function since the shifting is virtually equivalent to manual shifting by the shift lever. Also, engine braking effect can be fully utilized in sport mode.
In an automatic transmission provided with sport mode, an upshift or downshift can be requested by operation of the shift lever while upshift or downshift according to a vehicle driving condition such as vehicle speed and throttle valve opening is under operation.
In the case that a sport mode up-shifting request is detected during upshift, acceleration responsiveness may be deteriorated if shifting to the target shift-speed requested in the sport mode is delayed.
Also, in the case that a sport mode down-shifting request is detected during downshifting, engine braking effect may abruptly increase such that a shift-shock may be felt by a driver.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.